We propose an upgrade to our existing Superconducting QUantum Interference Device (SQUID) biomagnetometer (Tristan Model 637i) that will allow us (1) to increase the spatial resolution by installing additional channels;and (2) to add additional magnetic vector sensors in the center of the recording array. The upgraded instrument will have a greater ability to detect underlying bioelectrical activity with higher spatial resolution, to discriminate multiple sources of bioelectric activity and to identify subtle spatiotemporal variations in bioelectrical activity. The biomagnetic detection of gastrointestinal electrical activity offers the possibility of noninvasive diagnosis and characterization of disease states. The primary application of the upgraded device will be the detection of gastric and intestinal slow waves. In gastric studies in Project 1, the current instrumentation provides for the determination of an average propagation velocity, whereas the gastric propagation velocity exhibits a known spatial gradient. The increased spatial resolution of the modified instrument will allow us to compute the propagation velocity in different gastric regions. The detection of intestinal slow waves requires higher spatial resolution owing to (1) the relative size of the source compared with the gastric slow wave and (2) the presence of multiple adjacent small bowel segments in the vicinity of the segment of interest. The increased spatial resolution along with the new vector sensors will better enable us to distinguish these multiple sources, critical to the success of Project 2. Additionally, increased spatial resolution will improve our modeling abilities in Project 3. Finally, we will use the upgraded device to study the fetal magnetocardiogram.